Radar systems are useful for detecting, characterizing and monitoring various parameters associated with natural and/or man-made objects and are critical to both civilian and military operations. These systems typically transmit “beams” or electromagnetic (EM) signals intended to engage one or more objects or targets, and process reflected return signals (or echoes) for measuring spatial features, object identification and characterization. A radar echo return usually contains both signals generated from a desired target, as well as background clutter.
Certain environments are complicated by intentional deception methods designed to distract radar systems from an object or objects of interest. One such tactic is to flood the target scene with simple point-targets (also known as traffic decoys) to mask other more complex objects and/or pull off the radar's track beam away these objects, thus decreasing radar performance by hindering the system's ability to detect and track true targets in the presence of undesirable (which may also be known as false) target detections. Several aspects of a radar tracking system may be impacted in a variety of ways by such decoys. For example, depending on the proximity of the point-target(s) to the true target, proper construction of the true target response may be difficult, resulting in corrupt measurements that will be used downstream in order to make decisions about the objects being tracked, and subsequently how to allocate resources in the future.
Thus, the presence of traffic decoys may impact many different radar system functions. For example, the traffic decoys may affect radar system detection capability, as traffic decoys in close proximity to true targets may corrupt measurement values of true targets, affecting Tracking and Discrimination, and traffic decoys in close proximity to one another may generate measurement values representative of complex targets, affecting Tracking and Discrimination. In addition, the traffic decoys may affect radar system tracking functions, as Traffic decoy detections may be incorrectly correlated to true object tracks, resulting in measurement history corruption and/or causing true object tracks to exhibit kinematic behavior uncharacteristic of the true object. In addition, the traffic decoys may cause track steals, resulting in the loss or corruption of measurement history. Traffic decoys may also affect radar discrimination, as the presence of tracks on point scatters may result in misclassifying the true target as “non-true target” (leakage), and the presence of tracks on point scatters may result in misclassifying the point scatterers as “true target” (false alarms).
The presence of traffic decoys may also affect radar resource utilization and defense functions. With regard to radar resources, the traffic decoys may cause the radar system to incur additional beam shape losses, due to degraded ability to center beam on true target. In addition, traffic decoys may cause the need for additional radar resources by requiring beams on additional targets, and furthermore, the decoys may cause the need for additional or upgraded hardware for the system to process additional detections. With regard to defense functions, traffic decoys may cause an increased miss distance of interceptors, due to incorrect targeting, and may forces a defender to use additional interceptor inventory/more advanced designs (see KEI) to destroy expendable targets. In addition, the traffic decoys may force defenders to employ layered defenses to protect high value targets, and may mislead human-operated defenses, causing them to focus resources on expendable targets.
In the event of the deployment of decoy targets, an approach to screen out large quantities of undesirable point targets, i.e. spheres, in the presence of complex targets is desired. Several methods exist which attempt to discriminate between point targets and non-point targets. One such method takes advantage of the fact that spheres reflect the same response to transmitted pulses regardless of the incident polarization. This can be exploited with a radar system employing dual polarization, e.g. transmitting with linearly-polarized RF waves in the vertical direction and receiving in the horizontal. This would result in perfect cancellation for an ideal point target, while preserving the radar return for objects with complex scattering. However, this requires a radar system capable of dual polarization on transmit and receive, which can be a costly upgrade to the hardware if not already available.
A more simple and affordable approach using only available radar return data is desired for broader applicability to current radar platforms.